REF: General-MSR 11

Cutting Oils, Soaking Oils and Lubes

Everybody has a favorite cutting oil that used to be better than it is now or is out of production. There may have been recent performance issues with the existing oil or something has changed in the manufacturing process that precludes its use. new machines, additional contracts, changing environmental concerns, product cancellations, sustainability goals and other factors can all combine to limit the effectiveness or applicability of the current oil. 1)

Some metals are more difficult to machine than others. Stainless steel, exotic alloys and very hard metals demand a very high level of performance from the cutting oil. Other metals, like brass and aluminum, are easy to machine with general-purpose oils. 2)

Grinders, hand drills and deep-hole drilling machines require lighter viscosity oils for high rates of cooling and good chip and swarf flushing through-the-tool delivery and high-pressure application without foaming. 3)

Some cutting oils make great penetrating oil for soaking stuck bolts.

Straight oils

Non-emulsifiable and are used in an undiluted form, composed of a base mineral or petroleum oil and often contain polar lubricants such as fats, vegetable oils and esters as well as extreme pressure additives such as Chlorine, Sulphur and Phosphorus. Straight oils provide the best lubrication and the poorest cooling characteristics among cutting fluids. 4)

Synthetic Fluids

Contain no petroleum or mineral oil base and are formulated from alkaline inorganic and organic compounds along with additives for corrosion inhibition. They are generally used in a diluted form (usual concentration = 3 to 10%). Synthetic fluids often provide the best cooling performance among all cutting fluids. 5)

Soluble Oil Fluids

Form an emulsion when mixed with water. The concentrate consists of a base mineral oil and emulsifiers to help produce a stable emulsion. They are used in a diluted form (usual concentration = 3 to 10%) and provide good lubrication and heat transfer performance. They are widely used in industry and are the least expensive among all cutting fluids. 6)

Semi-synthetic fluids

Combination of synthetic and soluble oil fluids and has characteristics common to both types. The cost and heat transfer performance of semi-synthetic fluids lie between those of synthetic and soluble oil fluids. 7)